1. Field of the Invention
This invention relates to fixation devices and more particularly to arrangements for anchoring a ligament in a bone mass.
2. Prior Art
Until recently, in ligament repair and/or replacement surgery involving securing of one or both ligament ends to a bone mass have been accomplished utilizing staples, or like fixation devices, that are driven through or across the ligament and into the bone mass. Such ligament anchoring has involved connecting the ligament end to the bone mass exterior, requiring, for a knee cruciate ligament procedure, that the replacement ligament end or ends extend onto the periosteum or outside bone surface beyond a ligament tunnel with each end bent and secured onto the bone mass surface. Such ligament bending, of course, may result in a force concentration at that bend, weakening and potentially subjecting the ligament to rupture.
An earlier patent issued to two of the present inventors in a "Suture Anchor Assembly", U.S. Pat. No. 4,632,100, addresses anchoring a suture to a bone mass surface for joining a ligament thereto, but does not address securing a ligament in a ligament tunnel, as does the present invention. Another patent issued to two of the present inventors in a "Ligament Attachment Method and Apparatus", U.S. Pat. No. 4,772,286 does involve an endosteal fixation device for securing, at a certain tension, a ligament in a ligament tunnel. End coupling arrangements including a threaded flattened cone, expanding cone, and threaded cylindrical end anchors, that are taught by this patent, however, are structurally and functionally unlike the present invention. Also, still another invention of two of the present inventors in a "Ligament Anchor System", filed as a U.S. patent application, Ser. No. 289,728 is also an endosteal fixation system that includes a sleeve for turning in a tapped cortex, the sleeve to receive a footing turned therein that mounts a ligament. None of the inventions set out in these patents or in the patents cited therein or as were cited during the individual applications prosecutions, however, involve wedging a ligament bone block portion in a ligament tunnel as taught by the present invention.
The interference screw of the present invention is similar in construction to the anchor shown and described in the above-cited U.S. Pat. No. 4,632,100 of two of the present applicants, in that both involve a threaded cylindrical body with a forward fluted drill end. The patented anchor, of course, is for turning into a bone mass, whereas the interference screw of the present invention is cannulated for guided travel on a guide wire by a driver into a ligament tunnel, alongside a ligament fitted therein. The interference screw of the present invention is principally for wedging between a bone block portion of a ligament and tunnel wall, and is accordingly both structurally and functionally unlike the patented anchor.